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hERG Traf­fick­ing

hERG traf­fick­ing inhi­bi­tion on Human Embry­onic Kid­ney (HEK) cells

Long term expo­sure of drugs to ion chan­nel can lead to dis­rup­tion of the traf­fick­ing of the ion chan­nel to the cell sur­face mem­brane. It has been clearly demon­strated with the hERG chan­nel where many of the LQT2 muta­tions are caused by traf­fick­ing defects instead of mal­func­tion­ing of the cur­rent. By decreas­ing the num­ber of pro­teins that reach the sar­colemma, the num­ber of ion chan­nel pro­teins is dimin­ished (‘reduced hERG den­sity’) also lead­ing to less total cur­rent and hence to prob­lems in con­trol­ling repolarization.

Mea­sured para­me­ters:
  • Ampli­tude of the tail cur­rent upon repo­lar­iza­tion from –70mV to +60mV (pA)
  • Ampli­tude of the base cur­rent at –80mV (pA)
  • Inhi­bi­tion of hERG tail cur­rent amplitude (%)
  • IC50 value

At Phys­ioS­tim, the elec­tro­phys­i­o­log­i­cal con­se­quences of a pos­si­ble traf­fick­ing defect fol­low­ing a 24h incu­ba­tion with a com­pound at 1 con­cen­tra­tion will be recorded with the patch clamp tech­nique and com­pared to a con­trol group with incu­ba­tion dur­ing 24h in the pres­ence of the vehi­cle. Exper­i­ments are per­formed on n=10 per group. We do not mon­i­tor the chan­nel expres­sion at the cell sur­face, but we detect a pos­si­ble traf­fick­ing defects of chan­nel to the cell mem­brane by elec­tro­phys­i­o­log­i­cal recordings.

Ref­er­ence com­pounds or pos­i­tive con­trols:
  • quini­dine
  • sotalol
  • flu­ox­e­tine
  • amio­darone